The embodiments herein relate to valves and, more particularly, to a fuel metering valve, as well as a method of managing fuel in a metering valve.
Fuel metering valves may be employed in conjunction with a number of applications, including gas turbine engines, for example. Controlling combustion of gas turbine engines has proven to have significant advantages related to engine performance and fuel efficiencies. Electronically controlled fuel metering is one such avenue for improved engine performance and fuel efficiencies. Independent fuel scheduling using a solenoid activated device has been identified as having noteworthy advantages.
To gain significant benefits, the solenoid controlled fuel metering requires that it be located relatively close to burner nozzles. Two issues that arise using a solenoid activated fuel metering device, in a hot section, are “fuel coking” and contamination. Elevating fuel temperatures increase the varnish deposits that can block and bind mechanical components and is referred to as “fuel coking.” In addition, minute magnetic particles make up a significant portion of the fuel contaminates. Magnetic particles will attach to adjacent magnetic walls in the presence of a magnetic field and potentially create increased friction and binding.
Blocking and binding mechanical components is a particular consideration in jet turbine engine applications because jet fuel contains dissolved oxygen from simple exposure to atmospheric air. Reactions between dissolved oxygen and jet fuel lead to high molecular weight compounds which precipitate out of the fuel and form carbonatious deposits (i.e., “varnish”). These reactions are typically exponential with temperature. Therefore, the relatively high temperatures near the burner can raise concerns in terms of increased tendency for increased varnish formation, sometimes referred to as fuel “coking”. In addition, fuel contamination (e.g., magnetic particles) can be drawn from the fuel and attach to adjacent magnetic surfaces. A solenoid activated device requires a magnetic field to move and schedule fuel flow to the engine. The presence of a magnetic field presents a challenge to prevent the accumulation of magnetic particles that are constantly flowing thru the fuel stream.